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Saturday, March 7, 2009

'Catch' cancer? Yes, you can

A VERY close relative of mine has just come down with lymphoma. This is a cancer of the specific type of white blood cells called lymphocytes, which are part of the immune system.

Specifically, my relative has non-Hodgkin's lymphoma - indeed, a relapse of the disease he first had in 2006. Cancerous lymphocytes multiply very fast to crowd out healthy tissue and create lumps, which he recently noticed again.

The first time around, it was a very aggressive variant that spread to his brain. Yet he was cured, thanks to the efforts of the National Cancer Centre's doctors and nurses. Now it is back with a vengeance.

At lunch last Sunday, his 16-year-old son asked in a low voice: 'Can I catch it from Dad?' His mother had a benign breast lump two years ago and another one again recently. Though he had been assured by adults that cancers were not contagious, it seemed to him that tumours struck by households.

It is folk wisdom that you cannot catch cancer like a cold. However, a recent Johns Hopkins University study revealed that if you have had oral sex with six or more individuals, you are thrice more likely to get oral cancer. This is caused by the human papilloma virus (HPV).

Last month, the British Journal of Cancer reported that cancers of the anus, vulva and vagina have increased among 'baby boomers' because of increased HPV transmission among the age group that launched the sexual revolution of the 1960s.

All this is in addition to the fact that 99 per cent of all cancers of the cervix are caused by HPV, now the most common sexually transmitted disease. A recent study showed that 28.5 per cent and 50 per cent of first- and third-year United States female university students, respectively, who had had just one male sex partner were HPV-positive.

The HPV causes no symptoms and our immune systems generally clear it out of the body within two years. However, in 10 per cent of infected women, it persists to cause cervical cancer. In all these cases, the HPV genome actually gets incorporated into the human genome. It then switches off the human genes that make specific human proteins which suppress cancers from developing. When these proteins are not made, cancers erupt.

If sex can transmit HPV that causes cancer in an unfortunate minority, you can obviously 'catch' cancer, even if it takes time to develop. We do not want cancer patients treated like lepers of old. But this should not mean being skittish about taking the necessary steps - like being careful with food or eating utensils of a loved one with cancer - to prevent transmission, if any, of his or her disease.

Take the case of an outdoorsy Secondary 3 boy named Cao Yuanchi from Raffles Institution who suddenly developed leukaemia within days of completing an Outward Bound School course in January. The leukaemia caused fatal bleeding in his brain. Did he catch something outdoors that triggered the fatal leukaemia?

Yet if you could catch cancer like that, oncology doctors and nurses should have extraordinarily high cancer rates. They don't.

However, this could be because, first, you probably do not catch cancer viruses from the air; and second, these professionals are meticulous in handling patient body fluids, the possible vehicles of transmission of cancer viruses.

Take the Epstein-Barr virus now known to cause Hodgkin's lymphoma in previously healthy people, and non-Hodgkin's lymphoma in those with suppressed immunity like organ recipients. It also causes nasopharyngeal carcinoma, the nose cancer rare worldwide but common in Singapore, Malaysia and south China.

Transmitted by saliva, it also causes glandular fever, nicknamed the 'kissing disease' for obvious reasons. Yet the hospital dietitian advised my relative's wife to cook bigger portions. Her husband would then have more to eat and, for the sake of convenience, she could just consume the leftovers. No risk of catching his lymphoma, of course, she added.

The Epstein-Barr virus causes yet another lymphoma called Burkitt's, which usually appears as a jawbone lump that can double in size within 24 to 48 hours. The virus' genome is detected in 100 per cent of these cases, which usually occur in equatorial Africa.

Elsewhere, Burkitt's manifests mainly as abdominal masses. This week, local colorectal surgeon Francis Seow-Choen revealed in The Straits Times that he contracted it in 1964 when he was seven.

He obviously survived, Burkitt's being eminently treatable even back then. Not so non-Hodgkin's, which has a survival rate of only 51 per cent five years after diagnosis. If its spread, or that of nose cancer, say, may be prevented by being careful with food and body fluids, why not say so?

In fact, almost one in every five cancer cases is caused by infections, mainly viruses but also at least one food-borne bacterium called Helicobacter pylori that causes stomach cancer. There are also two food-borne parasites, the Thai- and Chinese-liver flukes, which cause cancer of the ducts that serve to drain bile from the liver into the intestines.

The takeaway lesson here for family members? Don't be politically correct unto death.

andyho@sph.com.sg

Daedalus (meaning "cunning worker" in Greek) was the man who built wings so he and his son Icarus could fly. As Icarus flew too close to the sun, his wings melted and he crashed to earth. Daedalus is a weekly column on the triumphs and challenges of science and technology.